The present invention relates to a dosing device of the type comprising a hollow punch which is dipped into the material to be dosed, thus taking a predetermined metered amount of such material, and subsequently discharging said metered amount inside a suitable container. More particularly, but not exclusively, the dosing device according to the present invention is used for the filling of gelatine capsules with a measured amount of a pharmaceutical substance.
There are known dosing devices which substantially comprise a tubular housing vertically movable up and down, a hollow punch secured to the lower end of said housing, an ejecting piston carried by a suitable piston rod and axially slidable at the interior of the hollow punch, and an actuating rod connected by its lower end to the upper end of the piston rod, so as to control the vertical movement of said piston inside the hollow punch. Usually, the connection between the lower end of the actuating rod and the upper end of the piston rod is obtained by screw means. For example, the upper end of the piston rod may be externally threaded and the lower end of the actuating rod correspondingly internally threaded.
The mentioned dosing devices, however, have the disadvantage that, whenever it is desired to disassemble the piston (and piston rod) from the dosing device, it is necessary to screw off the piston rod from the actuating rod, and this operation, particularly in the automatic machines containing a great number of dosing devices, requires time and skill, since an improper screwing operation may prejudice the exact positioning (centering, axial displacement) of the ejecting piston at the interior of the hollow punch. Disassembly of the piston from the actuating rod may be required for various reasons, such as replacement of a damaged piston, cleaning all the pistons of a machine, replacement of the entire set of pistons and hollow punches with another set having different dimensions.
According to the invention, there is provided a dosing device in which the connection between the lower end of the actuating rod and the upper end of the piston rod is a magnetic type connection. According to a preferred embodiment, a permanent magnet is provided at the lower end of the actuating rod there is provided a permanent magnet, while a pastille or disc of ferromagnetic material is provided at the upper end of the piston rod.
In this manner, the piston rod can be disassembled from the actuating rod simply by detaching the said two parts, with minimum effort, while their connection during the operation of the device is safely assured. Still in accordance with the invention, the contacting surfaces of the magnetic connection are constructed as flat surfaces, so that sliding of one surface relative to the other is permitted, thus assuring self-centering of the piston rod at the interior of the hollow punch, even in case of non-alignment of the axis of the tubular housing and of the said hollow punch.
The above and other objects of the invention will apprear from the following description of a preferred embodiment thereof, made with reference to the attached drawings.